Democrats and Republicans continue to raise serious questions about changes in state law that the leader of the Missouri Senate is proposing and a $100,000 campaign contribution he received from a prominent Joplin businessman who might benefit from the bill.

This week, a government watchdog group in Washington, D.C., weighed in and asked the U.S. attorney from these parts to investigate. The Campaign for Accountability wants to determine if Richard’s actions violated federal law that bars “pay to play” practices in which legislative favors are bestowed as a result of campaign donations.

We want answers, too. The U.S. attorney’s office should clear up yet another lingering ethics issue in the Missouri Capitol. And if Richard, the only person ever to lead both the state Senate and House, wanted to do the right thing, he’d spare his colleagues more ongoing embarrassment by stepping down for the remaining weeks of the 2017 session.

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Such a move would ease the pressure on Richard’s fellow senators to back the legislation he’s pushing that would make it more difficult for consumers to sue under the Missouri Merchandising Practices Act. The law is designed to stop deceptive and unfair business practices.

The change in the statute could benefit David Humphreys, owner of Tamko Building Products, which was sued in 2014 for selling defective shingles. The company denies the charge.

Here’s the rub: Richard filed his legislation in early December. Six days later, he received that six-figure check from Humphreys, and not long after that, the ethics wolves rightly started circling.

This week, Richard offered another statement vehemently denying any wrongdoing.

“These allegations are reckless and not true, and they will not deter me from doing the work of the people,” he said.

When the Senate leader responded last month to criticism over this controversy from state Rep. Mark Ellebracht, a Liberty Democrat, Richard said Ellebracht could “kiss my ass.”

That didn’t help matters. The optics on this issue are horrible. And we are amazed — even astonished — at the brazenness of some Missouri lawmakers who continue to engage in practices that raise serious questions of propriety, not to mention legality, especially given the checkered history of Missouri government. Many of those legislators are doggedly reluctant to pass ethics legislation that would help remove the taint that hovers over the Capitol like a dense fog.

Citizens have signaled in polls and at the ballot box that they want to wring big money out of the building. It was just in November — remember? — that 70 percent of voters agreed to slash the size of permissible campaign contributions.

President Donald Trump could help resolve serious questions about Richard’s actions if the president got about the business of hiring a new U.S. attorney for this area. It also would help if Missouri had an ethics commission with teeth instead of just soft gums. But none of that should derail or delay what needs to happen, and that’s a federal government investigation. Missouri deserves answers. The Richard issue “begs” for a grand jury investigation, as Dan Stevens, the head of the Campaign for Accountability, said.

Such a move would send a signal one more time that Missouri government is not for sale. That’s clearly a message that some lawmakers need to hear.